1. Field of the Invention
The present invention relates to a method for production of castings containing cast-in tubes from steel, where the castings comprise cast steel and where the steel tubes are cast-in with a superheated melt of cast steel and where the steel tubes are filled with a granular, highly thermal conductive, refractory material before the casting step.
2. Brief Description of the Background of the Invention Including Prior Art
Methods for production of castings containing cast-in tubes from steel are known for example used as cooling elements for the walls of metallurgical furnaces such as blast furnaces. Usually grey cast iron with varying graphite formation is used as a casting material for the cooling elements. The material for production of the cooling tubes has a defined steel composition depending on the function (compare German Patent Laid-open DES-AS No. 27 19 165, DE-No. 30 13 560, A 1). Based on the various liquidus temperatures of grey cast iron and of steel tube material no substantial problems of casting technique are encountered when casting around such steel tubes with grey cast iron. The steel tubes to be surrounded by cast material usually do not need a material to fill the tubes during casting, however, at any rate they are to be protected against carburization on the outside by a suitable covering.
However, if, instead of grey cast iron, cast steel is employed as the casting material to surround the steel tubes as described in German Laid-open Document DE-OS No. 2903104 for a cooling element for a metallurgical furnace, then there result substantial problems of casting technique and metallurgical problems for the casting around of tubes of steel. For elimination of these problems it is proposed in the above document DE-OS No. 2903104 to dispose bodies from steel or cast steel between the cooling tubes, which are to accept the super-heating heat of the liquid cast steel. In addition, the cooling tubes according to the state of the art are to be filled with a high melting, highly thermal conductive and granular material before casting around with cast steel. Zirconia and chromium oxide or a mixture of these materials are recited as materials suitable for this purpose. However, if cooling elements are produced according to this known method, then part of the cast-in tubes for guiding cooling liquid have leaks. In addition, the recited materials for filling the tubes are relatively expensive.